Air-cooled motor



Sept. 22', 1936. Q B CQATES 2,055,337

AIR-COOLED MOTOR Filed Jan. 4, 1953 ATTO RNEY Patented Sept. 22, 1936 rATENr orgies Ala-coman Moron Charles B. Coates, Cleveland, Ohio, assigner to Chicago Pneumatic Tool Company, New York, N. Y., a corporation ci New Jersey Application .anuary 4,

2 Claims.

The present invention relates to a cooling arrangement for motors and has particular application to electric motors exposed to sand, grit, etc. The general object of the invention is to cool a motor of the type described by means of circulating air but in a dust-proof manner.

Electric grinders used in foundries, and in similar industries where there is much sand and grit in the grinding rooms, are usually short lived. This is due to dirt being pulledinto the bearings and the windings, which destroy them in a comparatively short time. Motors of the portable type are usually air cooled, and the circulating air adds to the problem of keeping the dirt out of the bearings. An object of the present ini/en tion is to overcome this dimculty by making the windings and bearings fully enclosed and providing Ventilating means outside of the enclosure but in thermal contact with the motor stator.

Another object of the invention is to adapt a cooling system oi the type described, to be used in a machine tool which has a gear transmission or speed reduction unit on the same axis of the motor. It is old to cool an enclosed motor by means of a ian which drives the air in an axial direction through passages disposed about the periphery of the motor. If, in such a system, a gear reduction unit were disposed in line with the fan, the latter, being connected to atmosphere, would ordinarily cause the exposure of the gears and their bearings to the dust. In the present invention, however, the gear reduction unit, as well as the motor is protected in a novel manner, since both are enclosed separately.

A further object of the invention is to provide a fan construction which draws air from an axial passage, diverts the same inwardly toward the axis and then forces it out. The fan, by :forcing the air outwardly, rather than axially, permits the gear case to be of the same diameter as the motor.

Other objects and features of the invention will appear moreclearly from the following description, taken in connection with the accompanying drawing and appended claims.

The drawing shows, in a sectional view, the invention applied to a portable electric tool, such as a grinder. The motor housing 2 is cylindrical and has an integral back end 3, to which is bolted the switch case 4. The back end is apertured at 5 to receive the rotor shaft 6. Seated in a counterbore in the aperture 5 is the bearing 1 for the rotor shaft. The bearingis enclosed in an airtight manner by the plate 8, secured to the back end. The bearing may be lubricated either 1933, Seriali No. 65?,i96

(Ci. T33-86) through the oiler @i in the back end, or by packing the bearing enclosure with grease. The front end of the housing r2 is closed by the end wall or diaphragm i@ which receives the rotor shaft 6 with a close-running t. The housing 2, back end 3 and diaphragm i@ combine to form a totally-enclosed chamber for the motor, which comprises the stator i3 and rotor i2. The motor cables may pass from the switch case to the motor through a tight rubber gasket at ida.

Outside of the motor chamber, and keyed to the rotor shaft Si, is a fan it, having an annular groove i5 rotatably receiving a rib iii on the diaphragm i@ to form a labyrinth seal. The fan is disposed within avian housing iii which has a radial wall it. Cooperating with the wall it to form an enclosed chamber is an arbor housing or gear case 2t. The arbor housing and fan housing are secured to each other and to the motor housing 2 by means oi bolts iii and suitable check nts. The radial wall it is apertured to receive the front. bearing 23 for the rotor shaft t. In order to exclude dust from this bearing, the latter is sealed by a labyrinth connection Z4 formed by cooperating surfaces on the fan i4 and wall is respectively. Enclosed within the gear case 2G, may be any suitable system of gears such as the gear reduction unit 25 ior transmitting rotation from the rotor shaft i to the tool spindle 26.

The air cooling system comprises a series of ducts or passages, such as 2t, extending through the cylindrical walls of the motor housing 2 and leading from the back end of the housing to the chamber formed within the fan housing i8. The ian it is preferably made in one piece and consists of a series of blades to which is united a denector ring 30. The deilector ring has a sliding t on its periphery with the fan housing I8 and is spaced from the diaphragm it. The fan housing is provided with one or more radially extending openings Si, by means of which the fan blades communicate with the atmosphere.

In operation, the fan i4 rotates with the motor shaft 6 and draws air through the motor housing passages 28, which are in close contact with the stator core i3. The deector ring 30 diverts the air toward the motor axis, from whence the fan blades drive the air through the opening 3l. As will be apparent from the foregoing description none of the air passages is in oommunication with the inside of either the motor housing 2, the switch case 4, or the gear case 20. Even the bearings for the fan itself are protected by the labyrinth connections. As a result any sand or grit u thrown into the air by the grinder, will not cause injury to the parts of the machine.

The arrangement of the ian to draw air through .the passages 26 rather than drive it through, has

the advantage that the air is introduced to the machine at a point more remote from the grind- 1. A portable electric driven tool for grinding,

polishing, or the like, comprising a motor housing, a gear housing axially spaced thererom, a motor enclosed in said motor housing and surrounded by a peripheral wall thereof, said peripheral wall being constructed in one piece, a shaft connected to the motor and extending into the gear housing, the adjacent end walls of said housings providing vbearings supporting the shaft, a Ventilating passage extending along the peripheral wall of the motor housing, a ian mounted upon the motor shaft between said housings, the interiors of both housings being totally enclosed in a dust-proof manner and out of communication with the fan and ventilating passage, whereby cooling o the motor may be eected without blowing dust into the housings, the fan being in a housing having at its periphery an atmospheric port and another port communicating with the peripheral motor housing passage, said fan having a deiector adapted to cause lrst inward and then outward movement of air in circulating from one port to the other. 2. A portable electric driven tool for grinding, polishing, vor the like, comprising a motor housing, a gear housing axially spaced therefrom, a moto: enclosed in said motor housing, a shaft connected yto the motor and extending into the gear housing, the adjacent end walls of said housings providing bearings supporting the shaft. a Ventilating passage extending along the periphery of the motor \housing, a fan mounted upon the motor shaft between said housings, the interiors of both hous- 

